/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.stdlib.text.function;

import axil.api.AxilObject;
import axil.api.extend.Environment;
import axil.api.extend.Function;
import axil.api.extend.Parameters;
import axil.api.extend.Source;
import axil.stdlib.core.type.Nil;
import axil.stdlib.text.type.Str;

import static axil.framework.Functions.string;
import static axil.framework.Functions.unreachable;


/**
 * Trim a string of leading and/or trailing whitespace.
 *
 * 		trim(a-string)
 * 		trim(a-string, "left")
 * 		trim(a-string, "right")
 * 		trim(a-string, "both")
 */
public class Trim implements Function {
	private enum End {
		left,
		right,
		both
	}

	/**
	 * Execute this function with the given arguments. The Axil compiler will
	 * ensure that the number of arguments passed to the function are valid.
	 * If this function fails during execution for any reason, then an exception
	 * is thrown.
	 *
	 * @param env
	 * 	The environment in which the function is being invoked. The environment
	 * 	is never null.
	 *
	 * @param params
	 * 	The parameters to the function, which can be any Axil object. The values
	 * 	given are never null but may be the nil object (Axil.NIL).
	 *
	 * @param source
	 * 	The source which is the original of the code invoking this function.
	 *
	 * @return
	 * 	Returns any Axil object, but not null. Use the Axil.NIL object for a
	 * 	null value.
	 */
	public AxilObject eval(Environment env, Parameters params, Source source) {
		End end = End.both;
		AxilObject b = params.b();
		if (b != Nil.object) {
			end = End.valueOf(b.toString());
		}
		String text = params.a().toString();
		switch(end) {
		case left:
			final int size = text.length();
			for (int i = 0; i < size; i++) {
				if (! Character.isWhitespace(text.charAt(i))) {
					return string(text.substring(i));
				}
			}
			return Str.blank;

		case right:
			final int sz = text.length();
			for (int i = sz - 1; i >= 0; i--) {
				if (! Character.isWhitespace(text.charAt(i))) {
					return string(text.substring(0, i + 1));
				}
			}
			return Str.blank;

		case both:
			return string(text.trim());

		default:
			throw unreachable();
		}
	}
}
